Java tutorial
/** * Copyright (c) 2012, Thilo Planz. All rights reserved. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU Affero General Public License as * published by the Free Software Foundation, either version 3 of the * License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Affero General Public License for more details. * * You should have received a copy of the GNU Affero General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ package v7db.files.mongodb; import java.io.IOException; import java.util.ArrayList; import java.util.Date; import java.util.List; import v7db.files.spi.ContentPointer; import v7db.files.spi.ContentSHA; import v7db.files.spi.InlineContent; import v7db.files.spi.ReferenceTracking; import v7db.files.spi.StoredContent; import com.mongodb.BasicDBObject; import com.mongodb.DB; import com.mongodb.DBCollection; import com.mongodb.WriteConcern; import com.mongodb.WriteResult; /** * References are stored in a collection, with a document for each owner. * * <ul> * <li> <code>_id</code>: The ownerId as given by the application. * <li> <code>refs</code>: The sha hashes used by the ContentPointers from the * last updates in an array. * <li> <code>refHistory</code>: The sum of all previous and current entries in * <code>ref</code>. * <li><code>purge</code>: This field is added when the object is to be purged. * It contains the timestamp of that event. * </ul> * * */ public class MongoReferenceTracking implements ReferenceTracking { private final DBCollection refCollection; public final static String DEFAULT_REFERENCE_COLLECTION_NAME = "v7files.refs"; public MongoReferenceTracking(DB db) { this(db.getCollection(DEFAULT_REFERENCE_COLLECTION_NAME)); } public MongoReferenceTracking(DBCollection refCollection) { this.refCollection = refCollection; } public void purge(Object ownerId) throws IOException { refCollection.update(new BasicDBObject("_id", ownerId), new BasicDBObject("$set", new BasicDBObject("purge", new Date()))); } public void updateReferences(Object ownerId, ContentPointer... contents) throws IOException { List<byte[]> content = new ArrayList<byte[]>(); for (ContentPointer cp : contents) { if (cp instanceof InlineContent) continue; if (cp instanceof StoredContent) content.add(((StoredContent) cp).getBaseSHA()); else if (cp instanceof ContentSHA) content.add(((ContentSHA) cp).getSHA()); else throw new IllegalArgumentException(cp.getClass().getName()); } WriteResult r = refCollection.update(new BasicDBObject("_id", ownerId), new BasicDBObject("$set", new BasicDBObject("refs", content)).append("$addToSet", new BasicDBObject("refHistory", new BasicDBObject("$each", content))), false, false, WriteConcern.SAFE); if (r.getN() == 1) return; if (r.getN() != 0) throw new IllegalStateException(); refCollection.insert(WriteConcern.SAFE, new BasicDBObject("_id", ownerId).append("refs", content).append("refHistory", content)); } }